Drinking water before bed: good or bad for your sleep?

A few sips of water before bed is fine for most people, and a glass on the nightstand is handy if your mouth gets dry. A big glass in the last hour or so before bed is a common reason for waking up to pee, though, so the better plan is to drink most of your water earlier in the day and keep the evening to sips.

Bedtime water gets talked about as either a health secret or a sleep wrecker. It is neither. What it mostly decides is whether you are up at 3 AM.

What does drinking water before bed do?

Not as much as you might hope, in either direction.

Your body is well set up for a night without drinking. In many adults, levels of a hormone called vasopressin rise at night, telling the kidneys to make less urine while you sleep. You still lose some water overnight through your breath and skin, which is why most people wake a little behind and why a glass in the morning is such a good habit. But a healthy adult doesn't need a glass at bedtime to get through the night, and drinking one doesn't stock you up for tomorrow. Much of it simply turns into urine.

You may see claims online that a glass at bedtime protects your heart or flushes out toxins overnight. Treat them with caution: they are not backed by good evidence. If you have a heart or kidney condition, your doctor's advice on fluids is the one to follow.

Where a drink at night does help:

• You are thirsty. Lying awake thirsty is no better for sleep than getting up to pee. A few sips settles it.
• Your mouth gets dry. A glass on the nightstand saves a trip to the kitchen.
• It is part of winding down. A warm drink without caffeine can be a pleasant signal that the day is done. Just keep it small.
• You take medicine at night. Take it with as much water as the instructions say.

Will drinking water before bed make you wake up to pee?

Often, if it is a lot. A big glass at 10:45 PM is likely to be on its way through your kidneys around the time you are falling asleep, and you may meet it again at 2 AM.

Waking up at night to pee has a name, nocturia. Getting up once is common, especially as people get older, and for many it is nothing to worry about. Waking two or more times most nights is worth mentioning to a doctor. It has many possible causes, some about habits and some medical, and a doctor can help sort out which.

The habit causes are the ones you can test yourself:

• A big drink late in the evening. Water, tea, or a mug of chamomile: a large drink is a large drink, whatever is in it.
• Alcohol. It makes you pee more, and it tends to make sleep lighter and more broken in the second half of the night.
• Caffeine. It makes you pee a little more and can keep you awake. Tea and cola count, not just coffee. What time to stop drinking coffee for better sleep has a cutoff you can work out from your own bedtime.
• Making up for the day. Realizing at 9 PM that you have barely drunk anything, and fixing it all at once.

How long before bed should you stop drinking water?

There is no official cutoff. A common suggestion is to have your last proper drink an hour or two before bed, and only sips after that. If you go to bed at 11 PM, that puts your last full glass somewhere around 9 or 10.

Treat that as a starting point and test it. Night trips have more than one cause, and the only way to know what helps you is to change one thing for a week:

1. Move your last full glass earlier. Try two hours before bed instead of one.
2. Drop the evening alcohol or caffeine, if you have any, for the same week.
3. Pee right before you get into bed, even if you don't feel a strong need.
4. Note how often you wake to go. A line in the Notes app, or on paper by the bed, each morning.

If a week of earlier drinks makes no difference to how often you wake, the evening glass probably wasn't the cause, and it is worth talking to a doctor.

Front-load your water earlier in the day

The trick is not to drink less, just to drink earlier. If most of your water happens before dinner, the evening needs very little.

If you get to the evening and realize the day slipped by with hardly any water, have a glass or two in the early evening rather than at bedtime, and accept that you'll go to bed a little behind. A day like that is better fixed by a good glass in the morning than by a liter at 10:30. If it keeps happening, thirst and darker urine will tell you.

Dry mouth at night

Some people want water at bedtime because they wake with a dry mouth, not because they are thirsty. A few things help:

• A small glass on the nightstand, with a lid. Sips when you need them, without waking yourself fully.
• Sips, not a refill. If you wake and drink a whole glass at 3 AM, you may be up again at 5.
• Look at the room. Very dry air from heating or air conditioning makes a dry mouth more likely.

A dry mouth that sticks around, or snoring and waking unrefreshed, is worth raising with a dentist or doctor. Mouth breathing and some medicines are common reasons, and they are easy to check.

Let the evening wind down on its own

If your evenings end at the Mac, Notchpals can mark the switch from daytime drinking to winding down. Its reminders come from a crew of characters who take turns dropping out of the notch, and two kinds of character share this job. The Water characters do the daytime work: a first glass in the morning, a water reminder now and then until 8 PM, and one afternoon visit. After 8 PM they stop asking.

The evening belongs to the Sleep characters. Nod, a koala who naps twenty hours a day and recommends it, guards the way to bed like a bouncer. About an hour before your bedtime (set in Notchpals' Settings, and 11 PM unless you change it), Nod slides down from the notch to start the wind-down.

NodBedtime's coming. Last call for emails. Wrap it up, nice and easy.

Make it the cue for your last drink as well. Finish what is in the glass, refill the one on the nightstand, and go to the bathroom before you get into bed. A wind-down routine for screen workers has more ideas for that last hour.